update

.CondaPkg/env/Lib/dataclasses.py

@@ -1168,8 +1168,17 @@ def _dataclass_setstate(self, state):
 
 def _get_slots(cls):
     match cls.__dict__.get('__slots__'):
+        # `__dictoffset__` and `__weakrefoffset__` can tell us whether
+        # the base type has dict/weakref slots, in a way that works correctly
+        # for both Python classes and C extension types. Extension types
+        # don't use `__slots__` for slot creation
         case None:
-            return
+            slots = []
+            if getattr(cls, '__weakrefoffset__', -1) != 0:
+                slots.append('__weakref__')
+            if getattr(cls, '__dictoffset__', -1) != 0:
+                slots.append('__dict__')
+            yield from slots
         case str(slot):
             yield slot
         # Slots may be any iterable, but we cannot handle an iterator